Convert Pandas Column to Lowercase

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  • Post category:Pandas
  • Post last modified:January 9, 2024
  • Reading time:8 mins read

You can convert column values to lowercase in pandas DataFrame by using str.lower(), map(), apply() and lambda function. In this article, I will explain how to convert uppercase column values into lowercase column values of pandas DataFrame with examples.

1. Quick Examples of Convert Lowercase Column Values

If you are in a hurry, below are some quick examples of how to convert lowercase column values in DataFrame.


# Below are the quick examples

# Example 1: convert lowercase column using str.lower()
df['Courses'] = df['Courses'].str.lower()

# Example 2: convert lowercase column using apply()
df['Courses'] = df['Courses'].apply(str.lower)

# Example 3: Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())

# Example 4: Convert pandas column to lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)

Now, let’s create Pandas DataFrame using data from a Python dictionary, where the columns are CoursesFeeDuration and Discount.


import pandas as pd
import numpy as np
technologies= ({
    'Courses':["SPARK","PYSPARK","HADOOP","PANDAS"],
    'Fee' :[22000,25000,24000,26000],
    'Duration':['30days','50days','40days','60days'],
    'Discount':[1000,2300,2500,1400]
              })
df = pd.DataFrame(technologies)
print("Create DataFrame:\n", df)

Yields below output.

pandas lowercase column

2. Pandas Convert Column to Lowercase using str.lower()

We can use str.lower() function to convert Pandas DataFrame column values to lowercase. This is a function from Series hence you can easily apply this function to a specific column. This syntax will convert specified column values from uppercase to lowercase. Here we convert the column values and assign it back to the same column.


# convert lowercase column use str.lower()
df['Courses'] = df['Courses'].str.lower()
print("Convert Pandas column to lower case:\n", df)

Yields below output.

pandas lowercase column

3. Convert Pandas Column to Lowercase using apply()

Similarly, we can use apply() function to convert column values of a given DataFrame to lowercase. For that, we need to pass str.lower() function into apply() function and then, call the specified column of the given DataFrame. df['Courses']=df['Courses'].apply(str.lower) this syntax converts uppercase column values to lowercase column values.


# convert lowercase column use apply()
df['Courses'] = df['Courses'].apply(str.lower)
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

4. Use apply() & Lambda Function

Alternatively, we can pass the lambda function into apply() function we can convert specified column values of a given DataFrame from uppercase to lowercase. Here, the lambda expression is used to construct an anonymous function.


# Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

5. Use map() Function

we can use the map() function to convert column values of a given DataFrame from uppercase to lowercase. For that, we need to pass str.lower() function into the map() function and then, call the specified column of the given DataFrame. df['Courses']=df['Courses'].map(str.lower) this syntax converts uppercase column values to lowercase column values.


# Convert pandas column to lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)
print("Convert Pandas column to lower case:\n", df)

Yields the same output as above.

6. Complete Example For Lowercase Column Values


import pandas as pd
import numpy as np
technologies= ({
    'Courses':["SPARK","PYSPARK","HADOOP","PANDAS"],
    'Fee' :['22000','25000','24000','26000'],
    'Duration':['30days','50days','40days','60days'],
    'Discount':['1000','2300','2500','1400']
              })
df = pd.DataFrame(technologies)
print(df)

# convert lowercase column use str.lower()
df['Courses'] = df['Courses'].str.lower()
print(df)

# convert lowercase column use apply()
df['Courses'] = df['Courses'].apply(str.lower)
print(df)

# Use apply() & lambda function
df['Courses'].apply(lambda x: x.lower())
print(df)

# Convert pandas column to lowercase use map()
df['Courses'] = df['Courses'].map(str.lower)
print(df)

7. Conclusion

In this article, I have explained how to convert specified column values of a given DataFrame from uppercase to lowercase by using str.lower(), map(), apply(), and lambda function with examples.

Happy Learning !!

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References

Naveen (NNK)

Naveen (NNK) is a Data Engineer with 20+ years of experience in transforming data into actionable insights. Over the years, He has honed his expertise in designing, implementing, and maintaining data pipelines with frameworks like Apache Spark, PySpark, Pandas, R, Hive and Machine Learning. Naveen journey in the field of data engineering has been a continuous learning, innovation, and a strong commitment to data integrity. In this blog, he shares his experiences with the data as he come across. Follow Naveen @ LinkedIn and Medium

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